5 In this question you must show detailed reasoning.
Fig. 12 shows part of the graph of .
The tangent to the curve at the point meets the -axis at A and meets the -axis
at B .
Ois the origin.
Find the exact area of the triangle OAB .
To find the area of triangle OAB formed by the origin O, point A where the tangent meets the x-axis, and point B where the tangent meets the y-axis, we will follow these steps:
Find the derivative of the function to determine the slope of the tangent line at the point .
Use the point-slope form of the equation of the tangent line to find the equations of the lines that meet the axes.
Determine the coordinates of points A and B.
Calculate the area of triangle OAB using the coordinates of points O, A, and B.
Step 1: Find the derivative
The function is given by:
To find the derivative :
Now, we evaluate the derivative at :
So, the slope of the tangent line at the point is .
Step 2: Equation of the tangent line
Using the point-slope form of the equation of a line:
where and :
Multiplying through by 4 to eliminate the fraction:
Expanding this:
Rearranging gives:
Step 3: Find points A and B
Point A (x-axis intersection): Set :
Solving for :
Thus, point A is .
Point B (y-axis intersection): Set :
Thus, point B is .
Step 4: Calculate the area of triangle OAB
The vertices of triangle OAB are:
O:
A:
B:
The area of triangle OAB can be calculated using the formula:
Substituting the coordinates:
This simplifies to:
Thus, the exact area of triangle OAB is:
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Beyond the Answer
To find the exact area of triangle OAB formed by the origin O and points A and B where the tangent line meets the x-axis and y-axis respectively, we need to follow these steps:
Step 1: Find the derivative of
The function is given by . The derivative is calculated as follows:
Step 2: Evaluate the derivative at
Substituting :
Step 3: Write the equation of the tangent line
Using the point-slope form, the equation of the tangent line at the point is:
Rearranging gives:
Step 4: Find the x-intercept (point A)
Setting to find :
So, .
Step 5: Find the y-intercept (point B)
Setting to find :
So, .
Step 6: Area of triangle OAB
The vertices are , , and . The area of triangle OAB can be calculated using the formula: